                  Real time spectrogram
                  ---------------------

Introduction
------------

This directory contains both the source code and a pre-compiled 
binary of a program called 'rtspect' which is a
real time wide band spectrogram. This program operates by
taking the audio signal, analysing it using FFT code, 
and displaying it in a graphical form in real time,
with time along the x axis and frequency along the y axis.
There is menu control for screen size and frequency scale range.

This program should compile and run OK on any Silicon Graphics machine
with GL and audio capabilities. There are no guarantees of any sort. 
This program is not maintained in any way by anyone. It should not 
be used for financial gain of any form. 


How to compile
--------------

Compilation may not be necessary. To run the program, type

rtspect

If you do need to compile the code, first type

make


Helpful hints on use
--------------------

Use 'apanel' to control audio source and level.
Click on the right mouse button for menu options. Select screen
size, frequency axis range and axis visibility as required.

Note that the selection of frequency ranges operates relative to
the input frequency sampling rate. They are half, quarter and an 
eighth of this value. So if, for example, sampling
rate is 48KHz at the moment the program starts up, options for
frequency range will be 24KHz, 12KHz, and 6KHz.

The screen size options do not give you 
more resolution, they simply 'cheat' by repeating pixels 
an appropriate amount of times.
Big screen sizes will appear horrible and blotchy; small screen
sizes will appear finely detailed. But the actual resolution
is the same regardless of size (128 point).

To pause the display, keep the space bar held down. When
the space bar is released, the display will continue.

The program uses an automatic gain control. This cannot be turned
off.


The files
---------

An 'ls -l' should produce a listing similar to the one below.

-rw-r-xr--   1 dpr2     rtvd         449 Aug 18 00:09 Makefile
-rw-r-xr--   1 dpr2     rtvd        2341 Nov 10  1992 README
-rw-r-xr--   1 dpr2     rtvd         194 Nov  5  1992 fft.h
-rw-r-xr--   1 dpr2     rtvd       21084 Nov 10  1992 main.c
-rw-r-xr--   1 dpr2     rtvd       20008 Aug 18 00:06 main.o
-rw-r-xr--   1 dpr2     rtvd        5884 Nov  5  1992 power.c
-rw-r-xr--   1 dpr2     rtvd        4148 Aug 18 00:06 power.o
-rwxr-xr--   1 dpr2     rtvd       69808 Aug 18 00:07 rtspect

These files are :

	Makefile - Makefile for compiling code
	README 	- This file
	fft.h 	- Header file for fft routines
	main.c 	- Main chunk of code (basically everything except fft routines)
	main.o 	- Binary for main.c
	power.c - Source code for Fast Fourier Transform and Power spectrum
	power.o - Binary for power.c
	rtspect - The final, executable, binary


Libraries used
--------------

These include

	libgl_s		shared GL library - for graphics 
	libm		math library - for calculations
	libaudio	audio library - for audio handling


Authors
-------

Several people have contributed towards the code in this directory.
These include

	David S. Maynard 	- ex of Silicon Graphics Computer Systems, USA
	Bruce Karsh		- Silicon Graphics Computer Systems, USA

	Paul Danset		- pdanset@hitl.washington.edu
	David Rossiter		- dpr@ohm.york.ac.uk


Thanks also to Jim Ambras at Silicon Graphics for giving the OK for release.


David Rossiter  		Aug 18 1993
Electronics Department
University of York
York
YO1 5DD
ENGLAND
